Full feathering propeller



p 1953 D. BIERMANN Re. 24,530

FULL FEATHERING PROPELLER Original Filed Nov. 6, 1952 5 Sheets-Sheet 1INVENTOR.

DAVID BIERMANN BYE 1.4.0 141M ATTORNEYS Original Filed Nov. 6, 1952 FULLFEATHERING PROPELLER 3 Sheets-Sheet 2 4 FIG-2 so A i 22 5' 20 5 Q I \1 I42 6 4o 12? I 8 a ranem twie 34 /v \3 i 50 4 3" |4 I! o O W I V 52 r1 1O I I H INVENTOR.

DAVID BIERMANN BY J 27 ATTORNEYS P 1958 D. BIERMANN Re. 24,530

FULL FEATHERING PROPELLER Original Filed NOV. 6, 1 952 3 Sheets-Sheet 3l HM [Mink FIG-5 INVENTOR. DAVID BIERMANN BY W 'LM ATTORNEYS UnitedStates Patent Ofilice Re. 24,530 Reissued Sept. 2, 1.958

FULL FEATHERING PROPELLER David Biermann, Piqua, Ohio, assignor toHartzell Industries Inc., Piqua, Ohio, a corporation of Ohio OriginalNo. 2,722,985, dated November 8, 1955, Serial llo, 319,019, November 6,1952. Application for reissue January 11, 1956, Serial No. 558,606

9 Claims. (Cl. 170-16021) Matter enclosed in heavy brackets appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This invention relates to propellers for aircraft, particularly to apropeller having adjustable blades, more particularly to the fullfeathering of such a propeller and the method of operating thepropeller.

Adjustable pitch propellers are substantially standard equipment inmodern propeller driven aircraft and it occasionally becomes necessaryfor the pitch of a propeller of this nature to be increased to the pointWhere the propeller blade rests edgewise to the direction of flight ofthe aircraft which it drives and in which position the propeller is saidto be full feathered. This circumstance anses, for example, inconnection with a multi-engine craft when one or more of the enginesfail and it becomes necessary to fly the craft on the remaining engineor engines. At this time it is essential that the propeller blades ofthe engines not in operation be brought to a full feathered conditionwhereby wind resistance is greatly reduced, maklng it possible to fiythe craft with the reducedpower available, and also preventingwindmilling of the engines not n operation and which could result inserious difiicultics if the engines were, for example, leaking oil orincluded broken parts.

Heretofore, certain problems have been encountered in connection withthe full feathering of propellers in that they either do not featherfully or else the feathering operatlon required too great a time toaccomplish.

With the foregoing in mind it is a primary object of this mventron toprovide means for quickly bringing a propeller to full featheredcondition, While insuring that the propeller blades will halt in exactlythe right position to give absolutely full feathering.

Another object is to provide an arrangement which can be controlled fromthe pilots cabin for quickly and accurately accomplishing the fullfeathering of an adjustable pitch. propeller.

A still further object is the provision of an adjustable pitch propellerhaving an arrangement for effecting the full feathering thereofsubstantially instantaneously and which does not interfere in any Waywith the mechanism employed for adjusting the pitch of the propellerblade.

A still further object of this invention is to provide an adjustablepitch propeller in which the propeller is prevented from moving to afull feathered position under normal conditions of operation of thepropeller when it is brought to a halt by stopping. the driving enginetherefor.

A particular object of this invention is the provision of an adjustablepitch propeller having a spring action on the propellerblades urgingthem toward their feathered positie-n.

Another object of this invention is the provision of an adjustable pitchpropeller arrangement in which the control of the pitch of the propellerblade is accomplished by a new cooperation between the basic forcesacting on the propeller blade.

A' still further object of the present invention is the provision anadjustable pitch propeller in which centrifugal force is utilized incontrolling the pitch angle of the propcller blades, and which mcansz'sarranged to be. at its maximum eficctiveness when the propeller is incruising pitch, but which does not interfere with the featheringof thepropeller.

The foregoing objects and advantages will become more apparent uponreference. to the following description taken in connection with theaccompanying drawings in which:

Figure 1 is a partial sectional View showing the hub part of a propellerconstructed according to my invention and with the blades of thepropeller stopped in the maximum pitch position which they occupy whenthe engine has been brought to a halt in a normal manner.

Figure 2 is a view similar to Figure 1 but showing the propeller bladesin full feathered position.

Figure 3 is a plan view looking down on top of the propeller in theposition it occupies in Figure 1.

Figure 4 is a view like Figure 3 but shows the propeller in its Figure 2position.

Figure 5 is a diagrammatical view showing the hydraulic control systemfor adjusting. the pitch of the propeller as it appears when thepropeller is in normal operation.

Figure 6 is a view like Figure 5 but shows the hydraulic control systemas it is adjusted for bringing the propeller into a full featheredposition.

Referring to the drawings somewhat more in detail, the propelleraccording to the present invention comprises a central drive hub 10secured by means of a flange 12 thereon to the end of an enginecrankshaft 14 as by the cap screws 16. Hub 10 has radially projectingportions 18 which carry the thrust bearings 20 that are engaged by theclamp members 22, the outer ends of which clamp members grip the. innerends of propeller blades24.

A stationary piston 26 is connected with hub 10 and extends outwardlytherefrom and-has its outer end closed by a member 28 that includes astem portion 30 bored for slidably fitting on a tube 32. Tube 32 at itsleft end carries a collar 34 against which one end of spring 36 abuts,the other end of spring 36 bearing against the left side of member 28.

The right end of tube 32 has fastened thereto a. nut 38 which closes theend of the said tube 32 and also provides means for connecting hollowcylinder 40 to the end of the said tube. Cylinder 40 extends over theend of piston 26 and sealingly engages the same as by the packing means42.

Tube 32 is availed of for conducting fluid under pressure into cylinder40 by means of the port means 44 in the extreme right end of the tube.It will be apparent that a supply of fluid under pressure to cylinder 40will cause rightward movement thereof on piston 26 andv this will movetube 32. rightwardly carrying with it collar 34 whereby spring 36 iscompressed.

This movement of cylinder 40 is utilized for adjusting the pitch of thepropeller blades by links 46 which are pivoted at their one ends as at48 to cylinder 40 and at their other ends as at 50 to a point on clamp22 associated with the adjacent blade.

Each clamp member 22 also comprises a counter weight 52 attached to theclamp members and extending radially outwardly therefrom. These counterweights are arranged as will be seen in Figures 3 and 4 so as to extendsubstantially at right angles to the plane of the associated propellerblade.

It will be apparent that. the counter weights 52 will provide for atorque on their respective propeller blades tending to increase thepitch of the said blades Whenever the blades are positioned at greaterthan Zero pitch and less than full pitch; full pitch, of course, beingthe full of the blades toward increased pitch position is assisted bythe spring 36 so that at any time the propellers are rotating and theoil pressure is released from cylinder 40, blades will quickly move tomaximum pitch, or full feathered position.

Due to the fact that the useful centrifugal force developed varies asthe counter weights move, the useful angular range for each counterweight is considerably less than 90 and is actually considerably closerto 45 of rotation of the propeller blade.

Since the feathering of the propeller blade will require a range ofangular movement of at least 70 it will be apparent that if the usefulcentrifugal force developed by the counter weights is strongest duringthe cruising pitch range, then the torque on the blades developed bythese forces will be reduced substantially to zero as the blade is movedto feathered position, and may even pass through zero and commenceacting in the opposite direction.

Thus, while the spring means 36 operates with, or is assisted by, thecentrifugal force developed by the counter weights 52 to increase pitchwhen the propeller is at cruising angular range, these two forces mayactually oppose each other when the propeller is feathered.

The centrifugal force developed by each counter weight is responsive torotational speed, and is thus highest when the propeller is rotatingrapidly. However, when the propeller is being feathered its rotationalspeed reduces and the centrifugal force developed by each counter weightthus becomes smaller and smaller and the spring which is acting on thepropeller blade, namely, spring 36, becomes more and more the dominantforce.

In normal operation of the propeller it is desirable to prevent thepropeller from moving to maximum pitch position when the engine isbrought to a halt in the normal manner. In order to provide for thisfeature, the propeller construction of this invention has mounted oneach of the clamp members 22 a notch or apertured plate 54 adaptable toreceiving a plunger 56 that is carried in a sleeve 58 supported with aflange. A spring 60 urges each plunger 56 inwardly with a predeterminedthrust so that in normal operation when the engine is brought to agradual halt, the pins 56 will engage their plates 54 and will halt thepropeller blades in about their Figure 3 position. This gives thepropeller blades the desired pitch for again starting the engine undernormal operating conditions.

The stop pins 56 are adapted to throw out at relatively low speeds, forexample, 500 to 1000 R. P. M. and at speeds greater than that, the stopwill be disengaged so that the propeller can be adjusted to any desiredpitch, or can be full feathered substantially immediately.

The provision of the stop for the propeller blades also prevents thespring 36 from gradually forcing the propeller blades into fullfeathered position when the engine is brought to a halt and thus forcingthe oil out of the cylinder along leakage paths in the governormechanism and oil seals of the engine.

The governor mechanism by which fluid under pressure is supplied tocylinder 40 or exhaust therefrom may be of substantially anyconventional type and is illustrated diagrammatically in Figures and 6of the drawings.

In these views there is provided a control valve 70 to which pressurefluid is supplied by conduit 72 from a pump 74 that may be engine drivenor which may be driven by an auxiliary motor 76. The valve comprises avalve member 78 which in one position connects tube 32 with pressureline 72, in another position connects tube 32 with exhaust conduit 80leading to reservoir 82, and in a third position interrupts flow to orfrom tube 32 thereby entrapping the fluid in cylinder 40 and holding thepropeller blades in whatever position of adjustment they occupy at thattime.

A speed respective mechanism such as the flyball governor 84 adjustsvalve member 78 in accordance with the speed of the drive engine therebytending to maintain 4 a constant engine speed by adjustment of thepropeller pitch.

For effecting the instantaneous feathering of the propeller there isprovided cam 86 which may be manually operated from the pilots cabin bya lever 88 and which is effective when operated to force valve member 78to its Figure 6 position. With the valve member so shifted, the insideof cylinder 40 is connected directly with reservoir 82 and spring 36 iseffective for moving the propeller to full feathered position as rapidlyas the oil can be expelled through tube 32 and valve back to reservoir82. Normally this will take only about three seconds as contrasted toconventional feathering arrangements which normally require eight to tenseconds.

It will be appreciated that the act of feathering the propeller in themanner described is done while the craft is in flight and the propelleris rotating and that for this reason the stop plungers 56 will be intheir outer positions and thus will not engage the stop plates 54 andaccordingly will not interfere with the feathering operation. From theforegoing it will be seen that this invention provides for an adjustablepitch propeller having a normal maximum pitch stopped position of thepropeller blades which is entirely automatic in operation with manualmeans'being provided whereby there can be a substantially instantaneousfull feathering of the propeller so long as the propeller is rotatingabove a predetermined speed.

It will be understood that while the drawings illustrate the counterweights 52 so located that they lie in a plane extending at right anglesto the axis of rotation of the propeller when the blades are fullfeathered, these weights could occupy a somewhat different position andcould even be positioned rearwardly of the Figure 4 position when thepropeller blades were full feathered. This might come about because of asomewhat different location of the counter Weights 52 on the propellerblade to obtain the desired action for urging the blades towardincreased pitch position during rotation, or on account of the propellerblade being skewed from end to end whereby the full feathered positionthereof would be such that the counter Weight 52 was moved beyondcenter.

It will also be'understood that the specific governor control mechanismillustrated in the drawings and described in the specification is merelyexemplary and that the specific form which this governor might takewould be subject to wide variation with the essential thing being forthe governor to release fluid under pressure to the servo mechanism forthe propeller blades when it was desired to decrease the pitch thereof,and to release pressure fluid therefrom for increasing the said pitch.

In order to unfeather a propeller once it has been full feathered and itis desired to bring the propeller back into service, the governorcontrol is restored to its normal operating position which closes thegovernor by-pass valve. Thereafter, oil pressure is again establishedagainst the piston which moves the propeller blades and thisre-establishing of oil pressure can be accomplished in any of severaldifferent manners. For example, merely starting the engine will developpressure on the pump supplying fluid to the governor and this willdeliver pressure fluid to the piston thus unfeathering the blades of thepertaining propeller.

Still another manner of supplying fluid pressure to the piston forunfeathering the propeller would be to utilize oil from anauxiliary tankfilled with oil and air with the air under pressure. Such a tank couldbe maintained under pressure by fluid from the governor pump when thesaid pump was operating by way of a manually controlled valve.

It is also possible to employ pressure fluid from one governor pump forsupplying the piston of the propeller pertaining to another governorpump and this last arrangement would merely involve a connection of apipe between the governors with a simple control valve located therein.-

It will be apparent from the foregoing that the basic control of theblade angle is the result of a novel combination of a hydraulicactuator, a spring, and speed responsive counter weight means. Theseelements are combined in a particularly advantageous manner to providefor a simple and eflective control.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions, and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

I claim:

1. In combination in a variable pitch propeller with a drive enginetherefor; a hub, at least one blade extending radially from said hub androtatable thereon about its axis, spring means urging said blade towardmaximum, pitch position, a fluid motor associated with the hub and bladeresponsive to fluid pressure for urging the blade toward decreased pitchposition, a source of fluid pressure connected with said motor variabledirectly as the speed of the propeller, stop means between the hub andblade for stopping the propeller at a predetermined pitch when thepropeller is moving toward increased pitch position, said stop meansbecoming ineffective upon the propeller attaining a predetermined speedof rotation whereby exhausting of said fluid motor during rotation ofthe propeller above said predetermined speed will permit full featheringof the said blade by said spring means whereas upon reduction of fluidpressure to said motor by gradually slowing the propeller down bydeenergizing the drive engine for the propeller in a normal manner saidstop will become effective to halt said blade at said predeterminedpitch position.

2. In combination in a variable pitch propeller; a hub, at least oneblade extending radially from said hub, and supported for rotation onthe hub about the axis of the blade, a spring acting on the blade urgingit toward full feathered position, an abutment means for stopping theblade in its said full feathered position, a fluid motor connectedbetween the hub and the blade responsive to fluid pressure for movingthe blade toward decreased pitch position against the thrust of saidspring, a governor controlled fluid circuit for supplying pressure fluidto said motor under normal conditions, manual means selectively operablefor exhausting said motor to permit said spring to feather said blade,and stop means between the blade and the hub for stopping the blade in apredetermined maximum pitch position less than full feathered position,said stop means including an element responsive to centrifugal force asthe propeller rotates for making the said stop means ineffective whenthe propeller is rotating above a predetermined speed.

3. In combination in a variable pitch propeller having a hub and aradial blade rotatable thereon about the axis of the blade, a spring onthe blade operable to move the blade from zero pitch position to fullfeathered position, a fluid motor between the blade and the hubresponsive to fluid pressure to move the blade toward decreased pitchposition against the thrust of said spring, a plunger carried by saidhub and spring urged radially inwardly so that at a predeterminedrotational speed of said propeller the said plunger will move outwardly,and a stop element on said blade adapted for abutting the plunger onlyin its inward position whereby when the propeller is rotating and saidfluid motor is exhausted the spring will move the blade to fullfeathered position whereas, when the propeller is brought gradually to ahalt in the normal manner the said plunger and stop element will engageand halt the blade in a predetermined maximum pitch position.

4. In combination; a variable pitch propeller comprising a hub and bladeextending radially therefrom, said blade being rotatably supported onsaid hub for rotation about the axis of the blade, a piston elementmounted on said hub coaxially with the axis of rotation thereof, acylinder element movable on said piston element and connected with saidblade so that movementof the cylinder element by a supply of fluidthereto will decrease the pitch of said blade, a tube connected withsaid cylinder element and extending through said piston elementeoaxially therewith, a collar on the inner end of said tube, a springbearing between said collar and said piston element for urging the tubeand cylinder element in a direction to increase the pitch of said blade,abutment means for stopping the propeller blade in a full featheredposition, a stop element carried by said blade and extending radiallytherefrom, and a plunger carried by said hub and spring urged radiallyinwardly so as to engage said stop element in its innermost positiononly, whereby said plunger will throw outwardly when the propeller isrotating above a predetermined speed and said step element being solocated on said blade that when it engages said plunger, said blade willbe stopped in an intermediate pitch position.

5. In a variable pitch propeller having a hub and a blade extendingradially therefrom, said blade being rotatable on its axis on said hub,spring means acting on the blade urging it toward full featheredposition, fluid operable means connected between said blade and hubresponsive to fluid pressure for moving the blade toward decreased pitchposition, a stop element carried by the blade extending radiallytherefrom at the hub end thereof, a radially extending plunger carriedby the hub and having an innermost position where it will be engaged bysaid stop element, a spring urging said plunger inwardly so that at apredetermined speed of rotation of said propeller the plunger will moveoutwardly and out of the path of said step element, and said stopelement and plunger being so located that they will engage with theblade in an intermediate pitch position.

6. In a variable pitch propeller having a hub and a blade extendingradially therefrom, said blade being rotatable on its axis on said hub,spring means acting on the blade urging it toward full featheredposition, fluid operable means connected between said blade and hubresponsive to fluid pressure for moving the blade toward decreased pitchposition, a stop element carried by the blade extending radiallytherefrom at the hub end thereof, a radially extending plunger carriedby the hub and having an innermost position where it will be engaged bysaid stop element, a spring urging said plunger inwardly so that at apredetermined speed of rotation of said propeller the plunger will moveoutwardly and out of the path of said stop element, said stop elementand plunger being so located that they will engage with the blade in anintermediate pitch position, and said blade also being provided with acounterweight extending outwardly from one side in a directionsubstantially normal to the plane of said blade.

7. In a variable pitch propeller blade and counterweight combination asset forth in claim 6, wherein said counterweight extends from the camberside of said blade and is arranged to increase the pitch of the'bladewhen .the same is in the region 09 the take-ofi pitch and to urge theblade toward decreased pitch position when the counterweight occupies acenter of gravity position rearwardly of the plane of rotation of saidblade. 1

8. A full feathering variable pitch propeller blade structure comprisinga hub and blade extending radially therefrom, said blade being rotatablysupported on said hub for rotation about the axis of the blade, a fluidmotor comprising a piston element mounted on said hub coaxially with theaxis of rotation thereof, and a cylinder element movable on said pistonelement and connected with said blade so that movement of the cylinderelement by a supply of fluid thereto will decrease the pitch of saidblade, a tube connected with said cylinder element and extending throughsaid piston element coaxially therewith, a collar on the inner end ofsaid tube, a spring bearing between said collar and said piston elementfor urging the tube and cylinder element in a direction to increase thepitch of said blade to full feathering position, and said blade alsobeing provided witha counterweight rigidly fixed thereon and extendingoutwardly from one side in a direction substantially normal to the planeof said blade whereby the pitch of the blade is increased when the sameis in the region of the take-ofi pitch and coacts with said spring toincrease the pitch of the blade to full feathered position upon failureof said fluid supply.

9. A full feathering variable pitch propeller blade structure comprisinga hub and blade extending radially therefrom, said blade being rotatablysupported on said hub for rotation about the axis of the blade, a fluidmotor element connected to said blade and movable by a supply of fluidthereto for decreasing the pitch of said blade, a spring means acting onsaid blade to move the same to full feathered position, counterweightmeans extending 'stantly upon failure of the supply of fluid to saidfluid motor.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS Re. 20,283 Caldwell Mar. 9, 1937 2,105,843 Prestonet a1 Ian. 18, 1938 2,145,859 Caldwell Feb. 7, 1939 2,146,334 De CarlaFeb. 7, 1939 2,163,663 Caldwell June 27, 1939 2,304,153 Di Cesari Dec.8, 1942 2,427,586 Bierrnann Sept. 16, 1947 2,513,660 Martin et a1. July4, 1950

